All I want it to do is Arduino to repeatedly simulate keystroke/shortcut "A" when finger is moving clockwise (incrementing) and keystroke "B" when finger is moving counter-clockwise (decrementing). This is to be used as a "jogwheel" for an edit controller I'm building.

I had the idea that it might not be too much of a hassle to implement a scroll wheel with just an Arduino. You would only need one "send" pin and maybe four or five "receive" pins, all linked to the send pin with 1 M resistors. You would then send a "burst" (cycle of square waves) from the send pin, to each receive pin (in order). After reading each pin (see the reference) it would be flipped to an input with pinMode().

Hmmm... Quantum QWheel technology sounds exactly what I'm after. But I have no idea how to implement QT510 / QT511 / QT1106 in an Arduino design... Any thoughts?

My aim is to build an edit controller for Steinberg Cubase (or Nuendo). They've got excellent key mapping / macro facilities, so pretty much anything can be automated via keyboard shortcuts (fades, trimming, timing etc). As long as I could get a clickwheel / jogweel talking to Arduino, it would be a matter of minutes to assign the commands in Cubase. Unfortunately, my electronics knowledge is below basic. And I don't know how to connect this clickwheel to the Arduino Diecimila board I've got. I've worked with hardware audio editors in the past (such as the AMS Neve Audiofile SC) and I think a touchwheel / clickwheel would be a very attractive alternative.

It would be great if someone could help me stupid figure out how to connect this clickwheel to Arduino!

Does it have to be one of the Ipod wheels ?Couldn't you do the same with an ordinary rotary encoder, maybe with a large knob on it ?

Rotary encoder was my starting point. Which isn't bad, but I would my control surface to be as flat as possible. A touchwheel would be much more appropriate. Not necessarily an iPod wheel, but I thought since the component is so cheap it would be great if I could incorporate it into my design.

While on the subject, does anyone know of any jogwheel "wheel"/knob component manufacturers? I couldn't find a single one, anywhere. The biggest knob I found on Rapid Electronics was about 35mm diameter, and quite tall too (16mm), so not ideal. I could probably knick one from some old hifi or car stereo amplifier, but I was wondering if you guys knew of any jogwheel knobs sold separately, on their own?

If you can find a large enough knob for a rotary encoder you could just "embed" the encoder and knob in your box and have the top of the knob flush with the frontpanel of your box. This would of course make the box rather thick which might be just what you want to avoid :-)

I figured out a way to do that same sort of thing with the hall effect sensors in the brushless DC motor that's used in most types of CD-ROM and DVD-ROM drives. There are three hall-effect sensors, and with three comparators (TLC3704), I got six steps in a cycle. The cycle repeats six times per revolution, so it's ten degrees per step. If anyone's interested, I could write it up and convert it from AVR assembler to Arduino sketch code.

I've drawn up a first draft of the circuit diagram for the CD-ROM spinner control, using the Hall-effect sensors in the brushless DC motor. Here's a small version; follow the link to Flickr for bigger versions:

The three square symbols on the left are the three hall-effect sensors in the motor. Mine were connected in series by the PCB on the motor itself, and I just used two 100 Ohm resistors to send a small current through them. The bigger blobs on the diagram represent connections to the motor, and connections to the Arduino (any three digital inputs will do).